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HomeMy WebLinkAboutHARMONY TECH. PARK, HEWLETT-PACKARD - PDP - 12-97D - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT6. REFERENCES 1. "East Harmony Portion of McClellands Creek Master Drainage Plan Update — Final Report", ICON Engineering, August 1999. 2. "City of Fort Collins Stormwater Utility Storm Drainage Design Criteria and Construction Standards" 3. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria Manual", Volumes 1 and 2, dated March 1969, and Volume 3, dated September 1, 1999. 4. The Sear -Brown Group, "Final Drainage and Project Development Report for the Harmony Technology Park, First Filing, Fort Collins, Colorado", January 23, 1998. Preliminary Drainage Report Page 7 Harmony Technology Park, Second Filing November 15, 2000 management practices recommended in the "Urban Storm Drainage Criteria Manual — Volume 3"(1999) will also be used. 5.2 Drainage Concept Inlets proposed by the next submittal will collect runoff from the minor storm. The runoff will be intercepted by the inlets and conveyed in pipes to detention/water quality ponds. The minor storm washes the majority of pollutants from the site. The water quality ponds will allow the pollutants to settle out of the stormwater runoff before entering the storm drain within the future Rock Creek Road right-of-way. Runoff from the major storm (100-yr), within the right-of-way, will also be intercepted by inlets and carried in the stormwater collection system. Overflow from the 100-year storm within the right-of-way will be carried in overflow swales from the low points in the streets into the detention/water quality ponds. As shown on the drainage plan, two detention basins are currently being planed. The required and available stormwater detention and water quality volumes are noted in the attached calculations and on the drainage plan for this project. Note that the sub -basin discharges were modified from the drainage basin masterplan to make the detention areas work. As noted in the basin masterplan, the allowable discharge from any area is 0.5 cfs. On this site, the northern most sub -basin will have a discharge rate of 0.72 cfs. The large south pond will have a discharge rate of 0.43 cfs. The discharge rate for the south pond is based on the contributing area from the middle, south and west sub -basins. It is currently assumed that future development south and west of the proposed development will also drain to the common detention basin located just north of Rock Creek Drive. At the time of that development, upsizing of the southern most detention pond will be addressed. The final pond grading will include one foot of free board and a water quality volume. Currently, the groundwater appears to control the design. With the next submittal the design will be able to better address the concerns regarding ground water and this site. Preliminary Drainage Report Page 6 Harmony Technology Park, Second Filing November 15, 2000 Stormwater in the streets will be carried in the gutter to either an on -grade inlet or an inlet at a low point. The water collected by the inlets will be conveyed underground within the stormwater collection system. Stormwater pipes will carry runoff to detention/water quality ponds where sediment is allowed to settle. As previously mentioned, detention/water quality ponds will discharge into the stormwater collection system designed and constructed by the adjacent projects. Offsite flow from Celestica's site must be considered with this drainage plan. However, the runoff from the Celestica site will not be combined with the runoff collected from the Harmony Technology Park, Second Filing development. The re-routing of the Celestica site's outfall will connect to a new pipe located near the intersection of Rock Creek Road and Cambridge Drive. The new storm drain will be constructed by the developers located to the east and southeast of Harmony Technology Park, Second Filing. The engineer for that project is TST, Inc. Consulting Engineers. 4.2 Specific Details The quality of storm water discharged into the proposed storm drain, built by others, in Rock Creek Drive will be maintained on the site through the use new water quality structures. The structures may include outfall protection and possibly combined irrigation storage and detention ponds. The sizing of the water quality ponds will be designed to meet guidelines given in the Urban Storm Drainage Criteria Manual Volume 3 (1999). Details of the water quality pond sizing are included in Appendix D. The water quality pond outlets will be designed with final construction plans. The storm sewer system will be designed to require minimum maintenance. The City of Fort Collins will be responsible for maintenance of storm drainage facilities located within the public right-of-way and the drainage easements established with the next submittal. Easements will be provided for all drainage facilities. The easements are for accessibility during maintenance. 5. CONCLUSIONS 5.1 Compliance with Standards The storm drainage improvements designed by this development will meet the criteria set forth in the City of Fort Collins Storm Drainage Criteria manual. Water quality and best Preliminary Drainage Report Page 5 Harmony Technology Park, Second Filing November 15, 2000 1 1 3.5 Hydraulic Criteria Storm drain inlets and pipes will be designed prior to the next submittal to insure that the 1 proposed grading plan will provide adequate drainage and cover. This report will look at cover over the pipe and general serviceability based on approximate invert elevations at points of connection constructed by the adjacent property owners. Inlets will be sized to intercept the peak flow from the 10-year storm using City of Fort Collins storm drainage criteria. Storm drain pipes are sized to convey the maximum flow rate from the 10-year storm event. 1 The 10-year frequency is outlined in Section 5 of the City of Fort Collins storm drainage design criteria. The sizes will be determined by using the computer program StormCAD, developed by Haestad Methods, Inc. StormCAD considers whether a pipe is under inlet or outlet control and if the flow is uniform, varied, or pressurized and applies the appropriate equations (Manning's, Kutter's, Hazen -Williams etc). Hydraulic conditions considered by StormCAD include mild, steep, horizontal, or adverse slopes. StormCAD uses the standard step method of computing gradually varied water surface profiles to determine the hydraulic 1 grades. Headloss calculations are performed at the junctions using the standard method. The computer output files will be included with the future report. There are no major storm drainage channels proposed on the site. Overflow swales will be provided at all street low point locations. The overflow swales will be designed to convey the peak 100-year storm flows safely away from the streets. Sizes for the swales will be determined using the computer program Flowmaster. Flowmaster utilizes Manning's equation to calculate the swale capacities. Grading and erosion control design of the swales will be completed with final plans. hn 4. DRAINAGE FACILITY DESIGN 4.1 General Concept Parking areas and roof drains will drain to an on -site stormwater collection system. The on - site system will discharge to their respective detention ponds. From the detention pond, stormwater will enter a storm drain constructed by the engineer designing the improvements adjacent to the project. All landscaping adjacent to buildings will be graded away from the ' foundation with a minimum of a 2% slope or as required by the geotechnical report. Preliminary Drainage Report Page 4 ' Harmony Technology Park, Second Filing November 15, 2000 minimum of 10 feet horizontally from the out side of the water main to the outside of any storm drain or sanitary sewer. 3.3 Hydrological Criteria Runoff computations were prepared for the 100-year (major) storm frequency utilizing the Rational Method. The gross contributing area for the proposed development is approximately 61 acres. The contributing area is based on the area developed by this project including the area within the right-of-way to the centerline of the adjacent streets constructed and designed by others. The contributing area also includes the entire right-of-way and easement area of the streets designed and constructed by this project. Therefore, the sub - basins are, approximately 19 acres and 42 acres for the north area and the middle area respectively for this proposed project. These areas are greater than the maximum 5 acres allowed for the, Rational Method as stated in the City of Fort Collins stormwater management manual. The Rational Method is used for this 50% submittal as it is anticipated that this method will give conservative sizing for larger areas in comparison to other methods. As the site layout is fine-tuned, the computations will be revised to reflect the correct method, whether it is Rational Method or UDSWM2. This will be dependent on the final sub -basin layout and on -site grading. All hydrologic calculations associated with the sub -basins are included in Appendix B. The calculations sheets included provide time of concentration calculations and a summary of the design flows for all Sub -basins and Design Points associated with this site. Detention is required on this site. Therefore, preliminary discharge and storage calculations were done with this report to approximate detention basin sizes. 3.4 Street Capacity The street capacities have not been checked with this report since this submittal consists only of horizontal layout of streets and utilities. When the plans for this project are to a point where street slopes are known, gutter capacities will be checked. Gutter flow reduction factors will be utilized and the depth of flow in the streets will not exceed the maximum depth for a particular street classification as outlined in the City of Fort Collins design ■W criteria. Preliminary Drainage Report Page 3 Harmony Technology Park, Second Filing November 15, 2000 ' 2.2 Existing Sub -basin Description Historically, the site generally drains to the southeast. Soils in the sub -basins are Nunn Clay Loam, 1-3 percent slopes. A copy of the master plan basin maps and soils maps are included in Appendix "A". There is some offsite runoff from the west. The runoff from the Celestica site is currently collected and discharged to a combination of detention and retention ponds located along the ' south boundary of their property. In addition to the ponds there is a 100-year overflow which currently discharges to an open swale designed with the Celestica site. The Swale is located near the southwest corner of the Celestica site and runs generally west to east to the eastern most quarter line where the swale turns south and discharges to an existing irrigation ditch. In the "Final Drainage and Project Development Report for the Harmony Technology Park, First Filing", it is noted that when the property east of Celestica is developed, accommodations must be made to discharge stormwater to any collection system constructed by the new development. i3. DRAINAGE DESIGN CRITERIA 3.1 Regulations 1 This report and design is prepared to meet or exceed the City of Fort Collins storm drainage criteria and the requirements established by the McClellands Final Report Update, 1999. 3.2 Development Criteria Reference and Constraints ' The constraints of this site are the depth of the storm drain extended to this site by the adjacent projects and the depth of groundwater when designing detention ponds. Since the site is a commercial development, the storm frequency is 10-year for the minor storm and 100- year for the major storm. The required storm frequency is outlined in Table ' 3-1 of the City of Fort Collins stormwater drainage design criteria. Street encroachement by stormwater is outlined in section 4.2 of the previously mentioned design criteria. The proposed sanitary sewer and water utilities will be a minimum distance of 18" vertically and a minimum of 6 feet horizontally from the storm sewer. Water mains will be located a Preliminary Drainage Report Page 2 ' Harmony Technology Park, Second Filing November 15, 2000 1 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location Harmony Technology Park, Second Filing is a tract of land located in the northwest Quarter of Section 4, Township 6 North, Range 68 West of the 6" Principal Meridian, City of Fort Collins, Latimer County, Colorado. More specifically, the project is located near the southeast corner of the intersection of County Road 9 (Ziegler Road) and Harmony Road. The project is bounded on the north by Harmony Road, on the west by Technology Parkway, on the east by Cambridge Road and on the south by an unnamed street running generally east to west. 1.2 Description of Property Harmony Technology Park, Second Filing consists of two lots. Lot 1, the northern most lot, is 15.70 net acres. Lot 2, the southern lot, is 35.35 net acres. The development will consist mostly of market rate office space with moderate research and development and minimal manufacturing, if any. The project will consist of 6 proposed building envelopes in a campus setting. The land is currently used as farmland. Future development south and west of the proposed plat will create lots of approximately 16 and 35 net acres of similar type land use. However, of the 16 net acres, a large portion will be used for detention and water quality for the future development and for lot 2 of this proposed development. 2. DRAINAGE BASINS AND SUB -BASINS 11 2.1 Major Basin Description ' According to the City of Fort Collins Master Drainage Plan, this site lies in the McClellands/Mail Creek basin. In August 1999 the final report for the East Harmony I Portion of McClellands Creek Master Drainage Plan Update was completed for the City of Fort Collins. Copies of the Final Report's conclusion and a copy of the drainage basin map are included in the appendix of this report for reference. Preliminary Drainage Report Page t fHarmony Technology Park, Second Filing November 15, 2000 TABLE OF CONTENTS PAGE TABLE OF CONTENTS i 1. GENERAL LOCATION AND DESCRIPTION 1 1.1 Location.............................................................................................................................. 1 1.2 Description of Property....................................................................................................... 1 2. DRAINAGE BASINS AND SUB -BASINS 1 2.1 Major Basin Description..................................................................................................... 1 2.2 Existing Sub -basin Description........................................................................................... 2 3. DRAINAGE DESIGN CRITERIA 2 3.1 Regulations......................................................................................................................... 2 3.2 Development Criteria. Reference and Constraints............................................................... 2 3.3 Hydrological Criteria.....................................................................................:.................... 3 3.4 Street Capacity .................................................................................................................... 3 3.5 Hydraulic Criteria............................................................................................................... 4 4. DRAINAGE FACILITY DESIGN 4 4.1 General Concept.................................................................................................................. 4 4.2 Specific Details................................................................................................................... 5 5. CONCLUSIONS 5 5.1 Compliance with Standards................................................................................................ 5 5.2 Drainage Concept................................................................................................................ 6 6. REFERENCES APPENDIX A EXCERPTS FROM OTHER REPORTS APPENDIX B HYDROLOGIC CALCULATIONS APPENDIX C HYDRAULIC CALCULATIONS APPENDIX C WATER QUALITY POND DESIGN Preliminary Drainage Report (50%) Page i Harmony Technology Park, Second Filing November 15, 2000 November 15, 2000 ft) J•R ENGINEERING A Subsidiary of Westrian Mr. Basil Hamden City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, CO 80522-0580 Reference: Harmony Technology Park, Second Filing. 90% Stormwater Management Report Submittal #1 Mr. Hamden: On November 9, 2000, Mark West and I met with you in your office to discuss the Harmony Technology Park, Second Filing stormwater management report. We appreciated the opportunity to discuss the site's stormwater management with you. As we discussed during our November 9, 2000 meeting at your office, due to the complexity and the size of the Harmony Technology Park, Second Filing development, JR Engineering will be submitting the previous stormwater management report for the site with this 90% submittal. Currently we are designing the site to include parking lot surface detention to a maximum depth of 12-inches. The intention is to detain as much stromwater as possible on the surface of the parking areas. This will decrease the overall size of the detention ponds within the development. Stormwater quality will remain in ponds. The hydrologic analysis will be performed using the EPA Storm Water Management Model (SWMM). ' Our thoughts regarding this submittal were that rather than submitting incomplete information at this time we would continue to work on the design and submit a full report at a future date. We hope this submittal procedure is not inconveniencing you and meets ' your expectations after our previous discussion. If you have any questions or comments please call either Mark West or me at your convenience. ' Sincerely, 1 / John E. Tufte, P.E. ' Project Engineer JET/ ' X:\3920000.all\3926500\Drainage\90%Submittal\90% SWM Report Letter#l.doc ' 2620 East Prospect Road, Suite 190, Fort Collins, CO 80525 970491-9888 • Fax: 970-491-9984 • w Jrengureering.com PRELIMINARY DRAINAGE PLAN AND REPORT HARMONY TECHNOLOGY PARK SECOND FILING November 15, 2000 Prepared by JR ENGINEERING 2620 E. Prospect Rd., Suite 190 Fort Collins, Colorado 80525 (970)491-9888 Prepared for Hewlett Packard Fort Collins, CO Job Number 9265.00